Thermodynamic properties of naphthalene and uric acid in ethylene glycol-water mixtures

The solubility of naphthalene and uric acid was measured as function of temperature (5–45°C) in water(W)-ethylene glycol(EG) mixtures over the entire composition range. The molar solubility data were used to calculate transfer Gibbs energies G _tr ⁰ (WW-EG) (from water to water-ethylene glycol mixtures) and the temperature dependence of G⁰ was used to compute the corresponding transfer enthalpies and heat capacities. The thermodynamic quantities are interpreted in terms of two contributions; a cavity term which is estimated using the scaled particle theory (SPT) and a solute-solvent interaction term. The latter is inferred from comparisons involving the SPT results and the naphthalene data, or the data for naphthalene and uric acid. The solvation effects in W-EG mixtures are discussed with reference to thermodynamic properties of the solvent mixtures available from previous work.